Within a radius of less than a hundred metres, three other ringforts cluster around it, one 80 metres to the west, another 50 metres to the north-east, and a third 92 metres to the south-east. Ringforts, or raths, are the most common archaeological monument type in Ireland, circular enclosures built mainly during the early medieval period to enclose a farmstead and its inhabitants, defined by a bank of earth or stone and often an outer ditch. Finding four of them in such close proximity, on the same ridge in County Mayo, raises the kind of questions that records rarely answer.

The rath at Killedan sits on top of a ridge in pasture, close to the break of slope on the north-eastern side, and its builders were attentive to the lie of the land. The enclosure is roughly circular, about 25 metres in diameter, and the bank has been built up slightly on the north-east to compensate for the natural fall of ground, while on the opposite side the slope itself does much of the work, giving the outer face of the bank an external height of around 1.7 metres. The bank is not uniform around the circuit. On the northern arc it narrows considerably to about 1.4 metres and the outer face becomes almost vertical, with traces of stone facing visible. This irregularity seems to reflect a later practical intervention: the rath was absorbed into a field boundary system at some point, and the northern stretch was reshaped accordingly. A modern field fence now crosses the interior on a roughly north-south axis, and field clearance stones have been piled against the eastern side. There is a gap in the bank at the north-west, about 3.4 metres wide, which may mark the original entrance. Much of the north-eastern interior has disappeared under brambles and blackthorn scrub, which is spreading into the rest of the enclosure as well.